As semiconductor devices become faster and more powerful with each new generation, they also generate more heat during operation than their predecessors. The ability to dissipate this heat is a crucial factor in ensuring device reliability. As shown schematically in FIG. 1, a heat sink 99 is typically placed on the back side 91 of a semiconductor device 90 after the device is bonded to a substrate 95. In such an arrangement, a heat-dissipating structure is provided only on the exterior of device 90; heat generated within the device (generally in the active area, near the front side 92) is required to travel through the thickness of the device before it can be dissipated. There is a need for heat-dissipating structures which can be incorporated within a semiconductor device, and which can conduct heat efficiently away from the active area on the front side of the device.